Provided is an optical fiber connection component in which an optical waveguide of a planar lightwave circuit and an optical fiber can be connected after a process using SMT and reflow mounting technology. The optical fiber connection component includes: a plurality of fiber guide holes into which optical fibers are insertable at intervals equal to intervals of a plurality of optical waveguides of the planar lightwave circuit; and grooves for demarcating an area provided with the plurality of fiber guide holes and an area coated with an adhesive in an end surface to be joined with the planar lightwave circuit. The plurality of optical waveguides and the plurality of fiber guide holes are respectively aligned and fixed to the planar lightwave circuit with the adhesive in advance.
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1. An optical fiber connection component for connecting a plurality of optical waveguides of a planar lightwave circuit and a plurality of respective optical fibers, comprising:
a receptacle component having a plurality of fiber guide holes into which the plurality of optical fibers are insertable, the fiber guide holes formed by joining a first lower substrate formed with a plurality of v-grooves into which the optical fibers are insertable at intervals equal to intervals of the plurality of optical waveguides and a first upper substrate having a short length in an optical axis direction of the optical fiber; and
a pluggable component having a plurality of fiber guide holes into which the plurality of optical fibers are insertable, the fiber guide holes formed by joining a second lower substrate formed with a plurality of v-grooves into which the optical fibers are insertable at intervals equal to the intervals of the plurality of optical waveguides and a second upper substrate having a long length in the optical axis direction of the optical fiber,
wherein, in case that the v-grooves of the first lower substrate and the v-grooves of the second lower substrate are aligned and joined, a space which allows the optical fibers inserted into the v-grooves of the first lower substrate to be bent is formed between the first upper substrate and the second upper substrate.
2. The optical fiber connection component according to
the plurality of optical waveguides and the plurality of fiber guide holes are respectively aligned and fixed to the planar lightwave circuit with the adhesive in advance.
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The present invention relates to an optical fiber connection component and an optical device manufacturing method and more particularly to a connection component for connecting a planar lightwave circuit included in an optical module mounted on a BGA package and an optical fiber, and an optical device manufacturing method in which the optical module including the planar lightwave circuit is mounted on the BGA package.
In recent years, with the spread of the Internet of things (IoT) and the expansion of cloud services, communication traffic rapidly increases, and the large capacity of optical communication networks is in progress. Further, in parallel with the large capacity of optical communication networks, the economization is also in progress, and an optical transmission/reception module such as a coherent receiver and an optical device such as a multicast optical switch which are components are required to be reduced in cost and improved in mass productivity. As one approach to realize the economization of optical modules for communication, attention is paid to the mounting form of integrating optical devices on a ball grid arrays (BGA) package (for example, see Non-Patent Literatures 1 and 2).
A main advantage of integrating optical devices on the BGA package is that a method of mounting optical devices on a printed circuit board becomes excellent in mass productivity. In the related art, the optical devices are housed in a butterfly package or the like. The optical devices are placed one by one on the printed circuit board, and then mounted by fixing the positions by screwing and soldering many lead pins on the side surface of the package one by one to a wiring pattern on the circuit board. On the other hand, when the optical devices are housed in the BGA package, the optical devices are automatically mounted at a high speed on the printed circuit board by surface mounted technology (SMT) generally used in electronic devices, and then a plurality of solder balls on the bottom surface of the BGA can be soldered collectively by a reflow furnace.
When the optical devices are housed in the BGA package, a footprint on the printed circuit board can be reduced, and the electronic devices and the optical devices can be mounted densely, whereby excellent high frequency characteristics can be expected. Accordingly, in order to reduce the cost of the optical devices and improve the mass productivity, desirably, the optical devices integrated on the BGA package are mounted on the printed circuit board by reflow mounting technology. The examples of the application destination of the optical devices integrated on the BGA package include a coherent receiver, an optical transceiver, and a digital coherent transmission/reception module and the like.
Non-Patent Literature 1: H. Tanobe, Y. Kurata, Y. Nakanishi, H. Fukuyama, M. Itoh, and E. Yoshida, “Compact 100 Gb/s DP-QPSK integrated receiver module employing three-dimensional assembly technology,” OPTICS EXPRESS, Vol. 22, Issue 5, pp. 6108-6113 (2014)
Non-Patent Literature 2: C. Doerr, J. Heanue, L. Chen, R. Aroca, S. Azemati, G. Ali, G. McBrien, Li Chen, B. Guan, H. Zhang, X. Zhang, T. Nielsen, H. Mezghani, M. Mihnev, C. Yung, and M. Xu, “Silicon Photonics Coherent Transceiver in a Ball-Grid Array Package,” OFC2017, Th5D.5
However, in a case where the reflow mounting technology is applied to the optical devices integrated on the BGA package, in the configuration described in Non-Patent Literatures 1 and 2, the optical fiber connected to the planar lightwave circuit has the problem described below.
In a conventional optical module, a pigtail optical fiber of several ten cm is connected to the planar lightwave circuit with a UV adhesive. In the case of being automatically mounted at a high speed on the printed circuit board by general-purpose SMT, such a long pigtail optical fiber hinders the operation of the device. Further, the coating of the general-purpose connected pigtail optical fiber and a connector portion do not have heat resistance to withstand the reflow furnace at 260° C. Accordingly, in a state where the optical fiber is connected to the planar lightwave circuit of the optical module, it is difficult to realize the mounting method excellent in mass productivity by the SMT and reflow mounting technology.
In related art, in an optical waveguide of the planar lightwave circuit and a core wire of the optical fiber, the connection position is aligned on a six-axis alignment device with accuracy of 1 μm or less, and both are fixed with a UV adhesive. A process is also considered which connects the optical waveguide of the planar lightwave circuit and the position of the optical fiber by active alignment after the optical device is mounted on the printed circuit board. However, it is difficult to fix the printed circuit board to the alignment device, and it is difficult to perform accurate alignment in a state where a plurality of chips are mounted.
An object of the present invention is to provide an optical fiber connection component in which an optical waveguide of a planar lightwave circuit and an optical fiber can be connected after a process using SMT and reflow mounting technology and to provide an optical device manufacturing method in which the optical device can be reduced in cost and improved in mass productivity.
In order to achieve the object, one embodiment of the optical fiber connection component of the present invention includes: a plurality of fiber guide holes into which optical fibers are insertable at intervals equal to intervals of a plurality of optical waveguides of a planar lightwave circuit; and grooves for demarcating an area provided with the plurality of fiber guide holes and an area coated with an adhesive in an end surface to be joined with the planar lightwave circuit. The plurality of optical waveguides and the plurality of fiber guide holes are respectively aligned and fixed to the planar lightwave circuit with the adhesive in advance.
One embodiment of a manufacturing method of an optical device includes: a first step of fixing an optical fiber connection component to the planar lightwave circuit with the adhesive in a state where the plurality of optical waveguides are respectively aligned with the plurality of fiber guide holes, the optical fiber connection component having a plurality of fiber guide holes into which optical fibers are insertable at intervals equal to intervals of a plurality of optical waveguides of a planar lightwave circuit included in an optical module mounted on a BGA package; a second step of mounting the planar lightwave circuit on the BGA package to form the optical module; a third step of mounting the optical module on a PCB by SMT and fixing the optical module by reflow mounting technology; and a fourth step of inserting the optical fibers into the plurality of respective fiber guide holes of the optical fiber connection component.
According to the present invention, by using the optical fiber connection component having the plurality of fiber guide holes into which the optical fibers can be inserted, the optical waveguide of the planar lightwave circuit and the optical fiber can be connected after the process using the SMT and the reflow mounting technology. As a result, the optical device mounted with the optical module can be fully automatically mounted at a high speed, and the optical device can be reduced in cost and improved in mass productivity.
Hereafter, the embodiments of the present invention are described in detail with reference to the drawings. In this embodiment, a connection component of a receptacle structure capable of connecting optical fibers afterward is connected and fixed to an input/output part of a planar lightwave circuit by active alignment. Thereafter, an optical device is mounted on a printed circuit board (PCB) by general-purpose SMT and fixed by a reflow furnace. Then, the optical fibers are inserted into the connection component and connected to the planar lightwave circuit without performing alignment (no alignment). In this embodiment, a coherent receiver for connecting multi-core optical fibers is described as an example. However, the embodiments can be applied to an optical module which is connected with an optical receiver for connecting single-core optical fibers, an optical transmitter mounted with a light source, and in addition, another optical component such as an optical modulator through the optical fiber.
(Optical Fiber Connection Component)
In the optical module 101, a quartz-based planar lightwave circuit 112 mounted with a high speed photo-diode (PD) array 113, a trans impedance amplifier (TIA) 114 for amplifying the electric signal output of the PD, and a DSP 115 for signal processing are mounted on the BGA package 111. Each of these components is fixed onto the BGA package 111 with an adhesive excellent in heat resistance. The planar lightwave circuit 112 includes a 90° hybrid optical circuit, a polarization multiplexer/demultiplexer, and the like. The PD array 113 is mounted on the planar lightwave circuit 112 and is connected to a TIA 114 through a wire bonding 122.
A connection component 116 into which three optical fibers 104 can be inserted is connected to the input/output part of the planar lightwave circuit 112 with a UV adhesive.
In the end surface of the connection component 116, grooves 124a and 124b cut in an x-axis direction demarcate an area provided with a plurality of fiber guide holes and an area coated with the UV adhesives 123a and 123b as described below. The optical fiber 104 is inserted after fixing the connection component 116 to the planar lightwave circuit 112 in advance. Thus, the UV adhesive is prevented from flowing into a portion where the end surface of the optical waveguide 131 and the end surface of the optical fiber 104 abut on each other.
The optical module 101 mounted with the planar lightwave circuit 112 to which the connection component 116 is fixed is mounted on the PCB 100 by general-purpose SMT and are fixed by the reflow furnace. Then, a bare fiber portion of the optical fiber 104 is inserted into the connection component 116 in the direction of an arrow in the drawing. In a state where the end surface of the optical waveguide 131 and the end surface of the optical fiber 104 abut on each other, the coating of the optical fiber 104 and the connection component 116 are fixed with an adhesive.
The bare fiber can be inserted into the fiber guide hole, and further, two V-grooves are formed on both sides of the three V-grooves in order to reliably hold the bare fiber. In the joining of the lower glass plate 141 and the upper glass plate 142, the size of the fiber guide hole formed by the V-groove and the upper glass plate 142 changes depending on the thickness of the adhesive. In this regard, when the lower glass plate 141 and the upper glass plate 142 are joined, bare fibers are held in two V-grooves in advance. Thus, the size of the fiber guide hole, that is, the interval between the lower glass plate 141 and the upper glass plate 142 can be set to the interval suitable for insertion and holding of the bare fiber.
Incidentally, in the first embodiment, an example is described in which the optical fiber is held by a V-groove substrate (lower glass plate) and a presser plate (upper glass plate). However, instead of the V-groove, a square cross-sectional shape of the groove or a semicircular groove may be used. Further, the configuration may be made such that a hole into which the optical fiber can be inserted is provided in a glass block. Accordingly, the optical fiber connection component may be used as long as the component has the fiber guide holes into which the optical fibers can be inserted at intervals equal to the intervals of a plurality of optical waveguides of the planar lightwave circuit 112.
(Connection Method of Optical Fiber)
First, a process of connecting the planar lightwave circuit 112 and the connection component 116 is described. The planar lightwave circuit 112 and the connection component 116 with the inserted optical fibers 104 are fixed on the alignment device. An optical signal is input to the optical fiber 104, and alignment is made to have a maximum signal strength while monitoring the received signal output from the optical module 101 (active alignment). Thereafter, the UV adhesives 123a and 123b are applied to the outside of the grooves 124a and 124b of the end surface of the connection component 116 and then irradiated with UV light to harden. Finally, the optical fiber 104 is removed, and the planar lightwave circuit 112 and the connection component 116 are fixed in a state where the optical waveguide of the planar lightwave circuit 112 and the fiber guide hole of the connection component 116 are aligned.
Next, the planar lightwave circuit 112, the TIA 114, and the DSP 115 are fixed on the BGA package 111, and the PD array 113 and the TIA 114, the electrode of the TIA 114 and the electrode pad of the surface of the BGAA package 111, and the like are connected by the wire bonding 122. In this way, the optical module 101 mounted with the planar lightwave circuit 112 and the component such as the DSPs 102 and 103 are mounted on the PCB 100 by general-purpose SMT and is fixed by the reflow furnace. Thereafter, the optical fiber 104 is inserted into the connection component 116, and the optical fiber 104 is fixed with a UV adhesive in a state where the end surface of the bare fiber of the optical fiber abuts on the end surface of the planar lightwave circuit 112.
In this way, the optical connection component aligned with high accuracy by active alignment is fixed to the planar lightwave circuit. Thus, even when the optical fiber is inserted later without alignment, the optical connection with the connection position is made possible.
(Evaluation)
On the basis of the above results, it is confirmed that the connection form of this embodiment is adapted also to a digital coherent receiver without any problem. It is confirmed that the connection loss does not change between a case where the optical fiber array is connected to the optical waveguide after the active alignment and a case where the optical fiber guide is connected first, and the fiber is connected after reflow without alignment as in this embodiment. As a result, the optical module having the same optical characteristics as those of the conventional one, especially the excellent characteristics of the optical connection part can be realized while realizing the mounting method excellent in mass productivity by SMT and reflow mounting technology.
(Optical Fiber Connection Component)
In a second embodiment, an optical module having a connection component facilitating multi-core optical fiber connection is further described. In an optical switch module, in many cases, many optical fibers are connected to the input/output part of the planar lightwave circuit. For example, in a 16×16 optical switch, thirty-two cores of optical fibers are connected, and the connection efficiency is considerably poor in the method of inserting the optical fibers one by one into the connection component of the first embodiment. In this regard, in the second embodiment, an optical fiber connection component capable of collectively connecting the multi-core optical fibers is described.
A total of thirty-two input waveguides and output waveguides are included in the 16×16 multicast optical switch. In addition, two loop waveguides for alignment at the time of connecting the optical module and the optical fiber may be added for input and output. The end surfaces of these input/output waveguides and the loop waveguides are exposed to the end surface (xy plane) of the planar lightwave circuit 212. A connection component 216 capable of collectively inserting and connecting thirty-two cores of optical fibers is connected to the end surface with a UV adhesive. Incidentally, a roof plate 232 is a reinforcing member for enlarging an adhesion area for fixing the planar lightwave circuit 212 and the connection component 216.
The connection component 216 is configured by connecting a receptacle component and a pluggable component, which are described in order below.
Similarly to the first embodiment, grooves 224a and 224b formed by cutting the end surface of the receptacle component 251 in the x-axis direction demarcate an area provided with a plurality of fiber guide holes and an area coated with a UV adhesive. Thus, the UV adhesive is prevented from flowing into a portion where the end surface of the optical waveguide and the end surface of the optical fiber 204 abut on each other. The receptacle component 251 manufactured in this way is fixed to the end surface of the planar lightwave circuit 212.
Thirty-two bare fibers obtained by removing the coating of the optical fibers 204 are inserted into the V-grooves and are held by the V-grooves and the upper glass plate 244. As illustrated in
Incidentally, on the opposite side of the surface where the bare fiber protrudes, the coating of the optical fiber 204, the lower glass plate 243, and the upper glass plate 244 are fixed by a silicone-based soft adhesive 225, thereby protecting the boundary between the bare fiber and the coated fiber.
When the pluggable component 252 manufactured in this way is connected to the receptacle component 251 fixed to the optical module, the optical fiber arrays of thirty-two cores are connected collectively to form the structure of the connection component 216 illustrated in
(Connection Method of Optical Fiber)
Next, thirty-two bare fibers are arranged along the V-grooves of the lower glass plate 241 of the receptacle component 251, and the bare fibers of the pluggable component 252 are inserted into the receptacle component 251. The end surface of the lower glass plate 241 of the receptacle component 251 and the end surface of the lower glass plate 243 of the pluggable component 252 abut on each other and are fixed with a UV adhesive (
The protrusion amount of thirty-two bare fibers held by the pluggable component 252 from the upper glass plate 244 in the direction of the planar lightwave circuit 212 has variations of about several μm. Even when the connection interval between the end surface of the optical fiber and the end surface of the planar lightwave circuit is shifted by several μm, variations occur in the connection loss of about 0.1 dB. In this regard, the buckling gap 253 is provided to allow the bare fibers to be bent appropriately. Thus, all the end surfaces of the thirty-two cores of bare fibers can abut on the end surface of the input/output part of the planar lightwave circuit. Accordingly, it is possible to prevent variations in connection loss at the connection end surface.
An adhesive surface can be formed between the lower glass plate 241 of the receptacle component 251 and the lower glass plate 243 and the upper glass plate 244 of the pluggable component 252, thereby improving reliability.
(Evaluation)
The optical transmitter and the optical receiver are connected with the optical module assembled as described above to measure characteristics of the multicast optical switch. The 16-channel connection loss average is 0.3 dB/point, and the loss variation is 0.05 dB. It is confirmed that a connection loss value and a value of loss variation are equivalent to those of the optical module assembled by connecting the conventional optical fiber array to the planar lightwave circuit.
According to this embodiment, the general-purpose SMT and the reflow technology can be used, and similarly to the electronic device, the optical device in which the optical module including the planar lightwave circuit is mounted on the BGA package can be fully automatically mounted on the PCB at a high speed. Accordingly, the electronic devices and the optical devices can be densely mounted on one PCB.
Since the optical fiber may be inserted after the optical device is manufactured, the conveyance of the PCB on a manufacturing line is facilitated in a manufacturing process of the optical device. In addition, the packing of the optical device is facilitated and efficiency in a distribution process is improved.
Conventionally, the fiber array connected to the planar lightwave circuit is polished by aligning a glass block part and the fiber end surface, but such a polishing process is not required.
Yanagihara, Ai, Shikama, Kota, Asakawa, Shuichiro, Muranaka, Yusuke, Nishi, Hidetaka
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